A ballast tank is provided on a ship in order to stabilize the vessel. In order to perform this function, the ballast tank is charged with ballast water. Since there is a possibility of soiled or dirty water being introduced into the ballast tank, it is necessary or desirable to exchange such dirty ballast water with clean water.
Conventionally, the ballast water is exchanged by using a pump. This requires power as well as an operator to control the operation.
It is an object of the present invention to facilitate the exchange of ballast water.